The following information is provided to assist the reader to understand the devices, systems and methods disclosed below and the environment in which they will typically be used. The terms used herein are not intended to be limited to any particular narrow interpretation unless clearly stated otherwise in this document. References set forth herein may facilitate understanding of the devices, systems and method or the background thereof. The disclosures of all references cited herein are incorporated by reference.
Many devices have been developed in an attempt to prevent or minimize injury to a worker falling from a substantial height. For example, a number of devices (known alternatively as self-retracting or retracting lifelines, retracting lanyards, fall arrest blocks, etc.) have been developed that limit a worker's free fall distance to a specified distance and limit fall arresting forces to a specified value.
In general, most currently available retracting lifeline safety devices or systems include a number of common components. Typically, a housing or cover provides enclosure/protection for the internally housed components. The housing includes attached thereto a connector for anchoring the retracting lifeline to either the user or to a fixed anchor point. The connector must be capable of withstanding forces required to stop a falling body of a given mass in a given distance. Components of retracting lifeline system such as the lifeline and connectors can, for example, have an ultimate tensile load or minimum breaking strength of at least 4500 pounds.
A drum or spool around which a lifeline is coiled or spooled rotates within the housing. The drum is typically under adequate rotational tension to reel up excess extended lifeline without hindering the mobility of the user. Like the anchor connector and the other operative components of the retractable lifeline safety device, the drum is formed to withstand forces necessary to stop a falling body of a given mass in a given distance. The lanyard or lifeline is attached at one end thereof to the drum to allow the drum to reel in excess lifeline. The lifeline is attached at the other end thereof to either the user or to an anchorage point, whichever is not already attached to the housing.
Retracting lifeline systems also include a mechanism which locks (that is, prevents rotation of) the drum assembly of the retracting lifeline upon indication that a fall is occurring. For example, when the rope, cable or web being pulled from the retracting lifeline system causes the drum assembly to rotate above a certain angular velocity or experience an angular acceleration above a certain level, a brake mechanism can cause the drum assembly to suddenly lock.
Given the forces experienced by retracting lifeline systems upon sudden locking of drum rotation, the operational components of retracting lifeline system are typically manufactured from high-strength materials such as stainless steel to ensure locking, while withstanding the stresses associated therewith. In that regard, though the fall may be stopped upon actuation of the braking mechanism of a retracting lifeline system, the suddenness of the stop may cause injury to the user or produce higher than desirable stresses in one more components of the safety system. Energy or shock absorbing devices or systems are typically used to absorb energy experienced by the retracting lifeline system and the user.
In a tie-back application, a lifeline of a retracting lifeline system is wrapped around an acceptable anchorage structure and is connected back onto itself (via an end connector), creating a secure anchorage for the user. In currently available retracting lifeline systems, a substantial length of a strengthened or reinforced portion of the lifeline over which tie-back is permitted is maintained outside of the housing. For example, a sleeve of a durable and/or sacrificial material can be used to encase a length of lifeline extending from the housing to enable tie-back over the length of the sleeve. The thickness and stiffness of the sleeve and/or a stitched portion in the webbing prevents the sleeve from being drawn within the housing. Although it is safe to tie back over the length of the sleeved or reinforced portion of the lifeline, there is no guarantee that a user will not tie back up-line from that portion of the lifeline over which it is safe to tie back. Moreover, the substantial length of lifeline maintained outside of the housing (for example, 36 inches or more) creates a catching, snagging and/or tripping hazard. Further, the substantial length of lifeline maintained outside of the housing can result in an undesirable length of free fall in the case that a significant portion of the length outside the housing is unused in tie back to an anchor (for example, in the case of tie back to an anchor having a relatively small circumference)